Manufacture of cellulose acetate



2,010,822 MANUFACTURE OF CELLULOSE ACETATE Carl J. Malm, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporationof New York T No Drawing. Application September 16, 1931,

Serial N0. 563,230 g 3 Claims. (Cl. 260-101) This application is acontinuation-impart ofmy co-pending application Serial No. 336,922,filed February 1, 1929, now U. S. Patent No. 1,908,525. 1 v

The present invention relates to the pretreatment of cellulose withacetic acid and a chlorinated aliphatic hydrocarbon and then esterifyingthe pretreated cellulose. 1

One object of my invention is to utilize the bath in which cellulosehasbeen pretreated, to form the subsequent esterification bath'by merelyadding esterifying ingredients to it after the pretreatment of thecellulose has been completed. The amount of chlorinated aliphatichydrocarbon which is employed in the pretreatment bath together withtheorganic acid is preferably the amount of the chlorinated hydrocarbonwhich is desired the esterification bath so that there will be no wasteof this ingredient by using an excess in the pretreatment and so that itwill be unnecessary to add more of this chlorinated hydrocarbon at anytime after the pretreatment.

Of course, if additionalchlorinated hydrocarbon is preferred in certaincases, it may be added in compatible amounts providing it does notinterfere with the esterification.

The present invention is an improvement of the process disclosed in U.S. Patent No. 1,823,359

of H. LeB. Gray, which discloses a process of acetylating cellulose inwhich the cellulose is pretreated with acetic acid and an acid catalyst,at the end of which treatment the mass of material is pressed until theratio of acid to cellulose is approximately two to one. The cellulose isthen acetylated with a mixture of acetic anhydride and ethylenechloride.

I have now found a process of acetylating cellulose wherein theintermediate step of pressing out the pretreatment liquid is unnecessarybetween the pretreatment, and the esterification of the cellulose. Forexample by my invention the pressing operation between the pretreatmentand acetylation of the Gray application is unnecessary and can beeliminated so that a considerable saving in acetic acid which isnecessary in any one operation may be effected.

I have found that the process described in the Gray application,referred to above, may be improved by pretreating the cellulose with amixture of acetic acid and a chlorinated hydrocarbon, such aschloroform, ethylene dichlorid, methylene chloride, dichlorethylene,trichlorethylene,

or carbon tetrachlorid and then without pressing out any of the liquidabsorbed from the pretreatment bath, acetylating thepretreated celluloseby adding the acetylating materials to the pretreatment batch. I havefound that if the cellulose is pretreated with acetic acid together witha chlorinated hydrocarbon the acetic acid is evenly distributedthroughout the cotton and a uniform and eflicient pretreatment obtained.An acetylation catalyst, such as sulfuric acid may be added to thepretreatment mixture or it may be added to the acetic anhydride in theesterification step as desired, or it may even be present as an impurityin some of the reagents employed.

As pointed out above, intermediate steps between the pretreatment andthe esterification, such as for the removal of acetic acid areunnecessary in the performance of my invention.

The following example is an illustration of one embodiment of myinvention:

About25 lbs. of cotton are treated with a mixture of about 25 lbs. ofacetic acid and 175 lbs. of ethylene chloride for about 4 hours at about100 F. The mixture is then cooled to approximately F. and then aboutlbs. of

acetic anhydride containing about lb. of sulfuric acid is added thereto.The temperature is then allowed to rise slowly to a maximum of about F.when a viscous clear solution is obtained denoting completion of theacetylation.

The reaction mixture or dope produced, which comprises cellulose acetatedissolved in acetic acid and ethylene chloride, is preferably treated ina precipitating bath at a temperature at or above the boiling point ofethylene chloride. For example, the mass may be poured into desires afibrous acetylation process the amount of carbon tetrachloride need notbe limited to non-precipitating proportions, but may be employed insubstantial amounts; equal parts of carbon tetrachloride and glacialacetic acid in the pretreatment is preferred when using that particularchlorinated hydrocarbon.

Other modifications of my invention such as its use in the production ofesters having higher acid radicals, such as cellulose propionate,cellulose acetate butyrate, etc.,or the use'of other known acetylationcatalysts will be obvious to those skilled in the art and come withinthe contemplation of my invention.

I claim as my invention:

1. A process of acylating cellulose which comprises pretreating thecellulose with a bath comprising a fatty acid and ethylene chloride andsubsequently adding a fatty acid anhydrid thereto. t

2. A process of acylating cellulose which comprises pretreating thecellulose with a bath comprising acetic acid. and. ethylene chloride andsubsequently adding a fatty acid anhydrid thereto.

3. A process of acylating cellulose which comprises pretreating thecellulose with a bath comprising a fatty acid and ethylene chloride andsubsequently adding a fatty acid anhydrid together with a catalystthereto.

CARL J. MALM.

